Inflatable support structure



Nov. 9, 1965 D. D. MULLIN 3,

INFLATABLE SUPPORT STRUCTURE Filed Oct. 18, 1961 FIG. IO 64TIIIIIIIIIIIIIIIIb INVENTOR. DOYLE D. MULLIN ATTORNEY 3,217,325INFLATABLE SUPPORT STRUCTURE Doyle D. Mullin, Minneapolis, Minn.,assignor, by mesne assignments, to Litton Systems, Inc., Beverly Hills,Calif., a corporation of Maryland Filed Oct. 18, 1961, Ser. No. 145,83013 Claims. (Cl. 343-18) The present invention relates to a supportstructure and more particularly to an inflatable structure forsupporting a radar corner reflector.

Corner reflectors comprised of a plurality of radar reflecting surfacesare used for identifying the position of a person or an object which isin distress or lost on land or at sea. These types of reflectors areused so that the lost person or object can be located by means of asearch party in an airplane, ship, or from the ground. In addition, byfloating a plurality of such reflectors in a body of water or in theatmosphere, or by orbiting them in space, by suitable means, they mightbe effectively used as a decoy system. As used herein, the term spaceexcludes the atmosphere surrounding the earth.

Corner reflectors of this nature have been constructed by connectingtogether a plurality of plane surfaces made of rigid material such assheet metal; by connecting together a number of panels made of aflexible, collapsible light-weight material having a reflecting materialadhered thereto; or by connecting together a number of panels made of aflexible, collapsible metallic fabric. The latter two types ofreflectors require the use of a rigid framework or other supportstructure for maintaining the reflector in a proper reflectingcondition. In addition, if the reflector is used on water, some meansmust be provided for maintaining the reflector above the surface of thewater.

Various types of structures are used to effectively support a cornerreflector and maintain it in a proper refleeting condition. According tothe known state of the art, collapsible support structures constructedof metallic or other rigid components, and inflatable supportstructures, such as spherical balloons constructed of a lightweight,gas-impervious material, are most commonly used to support a cornerreflector. Neither of these support structures are entirelysatisfactory. For example, a metallic support structure because of itsweight is limited regarding the environment of its proposed use, andunless a light-weight material is used, the structure may become undulyheavy. On the other hand, a spherical balloon is diflicult to make,especially if the balloon is formed by securing together a plurality ofgores having curved edges; in addition, such a balloon requires arelatively large volume of gas to inflate it, therefore, its use is bestsuited to small sizes.

Accordingly, one object of the present invention is to provide animproved support structure.

Another object is to provide an inflatable structure for supporting aradar corner reflector.

Still another object is to provide an inflatable support structure for acorner reflector which is easy and inexpensive to make, and which issimple in construction.

A further object is to provide an inflatable support structure for apliable, collapsible radar corner reflector which may be initiallystored in a collapsed condition and thereafter inflated to an erectedand rigid condition.

A still further object is to provide an inflatable support structure fora radar corner reflector which may be 3,217,325 Patented Nov. 9, 1965used in any environment, which is light in weight and which requires aminimum amount of inflation medium to inflate it and maintain it in anerected condition.

In general, the support structure of this invention is comprised ofthree square-shaped inflatable tubes having a desired cross-sectionalarea, which are connected together to form a structure for supporting aradar corner reflector. The inflatable tubes are connected to each otherby securing their respective corners together in such a manner that asupport structure having six corners results. A flexible cornerreflector, having six outer apices and a plurality of reflectingsurfaces, is positioned within the structure and connected to the sixcorners of the structure so that when the structure is filled with aninflation medium, the reflecting surfaces become taut and form aplurality of trihedrons. The surfaces of each trihedron being mutuallyperpendicular to each other.

Other objects and advantages of the invention will become apparent froma consideration of the following specification and drawings, wherein:

FIGURE 1 is a partial sectional elevational view of a deflated supportstructure folded and stored in a suitable container.

FIG. 2 is a partial schematic perspective view of the support structurefully inflated with an inflation medium, and having a corner reflectorattached.

FIG. 3 is a perspective view of the invention illustrated in FIG. 2 butviewed from a different position.

FIG. 4 is a partial schematic view taken along line 4-4 of FIG. 2,illustrating one way of connecting two corners of the support structuretogether.

FIG. 5 is an enlarged partial sectional view taken along line 5-5 ofFIGURE 4.

FIG. 6 is a cross-sectional view of a pressure beam taken along line 6-6of FIG. 2.

FIG. 7 is a cross-sectional view similar to FIG. 6 but showing thepressure beam in a deflated condition.

FIG. 8 is a partial schematic view illustrating another embodiment ofconnecting two corners of the inflatable structure together.

FIG. 9 is a partial sectional view taken along line 9-9 of FIG. 8.

FIG. 10 is an enlarged partial sectional view taken along line 1010 ofFIG. 9.

FIGURE 1 illustrates a support structure 10 in a deflated and collapsedcondition, and folded into a container 12, for storage prior to use.

FIGURE 2 shows the support structure 10 in an inflated and rigidcondition, after it has been filled with an inflation medium. In thisconnection, the particular type of inflation medium and inflation deviceused might vary. For example, a pressurized container (not shown)containing a gaseous medium might be used, or the structure might beinflated by using a sublimating substance. On the other hand, it may bepreferred to inflate the structure with a hardenable foam substance sothat a rigid support structure is formed after the foam hardens. Foamsubstances of this nature are well known in the art and will not bedescribed in detail.

The support structure 10 is shown supporting a flexible, collapsiblecorner reflector 14. As stated hereinbefore, such units might be usedfor decoy purposes, by floating a number of them on a body of water. Itis also envisioned that the invention might be used in the atmosphere aswell. For example, a plurality of the reflecting units might be droppedfrom a space vehicle,

and as it floats toward the earth, it would serve as an effective decoysystem. In addition, it is conceivable that a plurality of such unitsmight be orbited in space. Furthermore, while the inflatable structure10 is shown in combination with a radar corner reflector 14, it is notintended that the use of the invention should be limited to onlysupporting corner reflectors, as it is envisioned that the inflatablestructure might be effectively used for supporting other objects aswell. For purposes of illustration, however, the invention will bedescribed in combination with a corner reflector.

The support structure 10 is comprised of three separate tubular membersor pressure beams 16, 18, and 20, preferably having a deflatedcross-sectional area as shown in FIG. 7, and a circular cross-sectionalarea when inflated, as shown in FIG. 6. The two ends of each pressurebeam are connected together to form a continuous tube. This connectionis made by butting the two ends of the tube together and thereaftersealing or bonding a strip of material 22 over the two ends. The threepressure beams are connected together at their respective corners asshown in FIG. 2 to form a support structure having six corners 24, 26,28, 30, 32, and 34. Each pressure beam when connected to the other twopressure beams is formed into the shape of a square, note particularlypressure beam 16 in FIG. 2. The three pressure beams when connectedtogether form eight equilateralshaped triangles, note FIG. 3, and thestructure when inflated with a gaseous medium may be positioned on anyone of the eight triangles and still provide a suitable base for thesupport structure. An alternative method of forming the structure 10would be to connect the pressure beams 16, 18, and 20 together at theirrespective corners before each pressure beam is formed into a continoustube as shown at 22.

The inflatable structure 10 is shown supporting a corner reflector 14,comprised of a plurality of reflecting surfaces, designated generally byreference numeral 36. The reflector is attached to the support structureby suitable means such as tie-strings 37. The reflector is preferablycomprised of a flexible, collapsible, reflecting mesh-type material orthe like, which may be conveniently folded along with the supportstructure for storage during nonuse. It is however, also envisioned thatthe reflector might be constructed of a rigid material, such as sheetmetal, as well. The corner reflector 14 is comprised of eight trihedronsin which each is provided with three mutually perpendicular reflectingsurfaces 36 which meet at an inner apex 38. The inner apices of eachtrihedron are symmetrically positioned with respect to a common center.The reflector 14 includes six outer corners or apices which are adaptedto be attached to the corners of the support structure 10.

The pressure beams are constructed of any suitable, non-extensible,light-weight, gas impervious material, such as a nylon fabric coatedwith polyurethane, vinyl or the like; or a thermoplastic, such apolyethylene. The pressure beams are infiatably connected together attheir corners so that the entire structure is inflatable through asingle valve 40. The specific connection between the two corners dependsupon the type of material used, the amount of internal pressure, and thelike. As stated above, inflation of the structure 10 might beaccomplished by any commercially available means, such as a pressurizedcontainer provided with valve means for inflating the structure at adesired time, and will not be described in detail.

FIGURES 4 and 5 illustrate one method of inflatably connecting twocorners of two pressure beams together. In this embodiment, the supportstructure is constructed of a fabric type material. The pressure beamsare connected together by superimposing a first pressure beam 20 over asecond pressure beam 18, and at right angles to it. As noted in FIG. 5,the pressure beam 20 has a top surface 42, and a bottom surface 44 whichis provided with an opening 46. The pressure beam 18 on the other hand,has a top surface 48 which is provided with an opening 52, and a bottomsurface 50. In this connection, note that while the pressure beamsillustrated in FIGURES 4 and 5 are shown in an inflated condition, theyare connected together While they are in a deflated condition as shownin FIG. 7. The pressure beam 20 is superimposed over the pressure beam18 so that the openings 46 and 52 are in alignment. The two surfaces 44and 48 are adhered together by means of a suitable adhesive 54 which isplaced around the openings 46 and 52. The adhesive 54 not only securesthe pressure beams together, but also provides a gas tight connectionbetween the two surfaces. Four bolts 56, provided with gaskets 58, and anut and washer assembly 60 are provided to more securely connect the twopressure beams together. As the gaseous medium is forced into thesupport structure through the valve 40, the gaseous medium flows fromone pressure beam to the other until a uniform pressure is attainedthroughout the entire support structure. It may be preferred to provideinflatable connections as described above at each corner of thestructure. On the other hand, if desired, only two such connections needbe used; that is one inflatable connection at corner 26 which connectspressure beams 18 and 20 together, and a similar connection at corner 28which connects pressure beams 16 and 18 together (note FIGURE 2). Notethat the valve is positioned between corners 26 and 28.

As illustrated in FIG. 3, two corners of each pressure beam areconnected to two corners of a second and third pressure beam, so that asthe support structure becomes fully inflated, the three pressure beams16, 18 and 20 each form a square-shaped member, and a six corneredsupport structure results.

The embodiment depicted in FIGURES 8 and 9 illustrates a supportstructure constructed of a heat scalable thermoplastic, and morespecifically, the manner of inflatably connecting the corners of such astructure together. A first heat-scalable pressure beam is superimposedover a second heat-sealable pressure beam 62, and at right angles to it.The pressure beam 60 has a top surfaces 64 and a bottom surface 66 whichis provided with an opening 68 (note FIG. 10). The pressure beam 62 hasa top surface 70 which is provided with an opening 74, and a bottomsurface 72. In this connection, note that while the pressure beams areagain shown in an inflated condition in FIGURES 8 and 9, they areconnected together while they are in a deflated condition and preferablybefore each pressure beam is formed into a continuous tube. The pressurebeam 60 is superimposed over the pressure beam 62 so that the twoopenings are in alignment. A component, designated generally byreference numeral 76 is provided in at least two corners of thesupportstructure 10 for permitting the passage of a gaseous medium fromone pressure beam to the other.

The component 76 includes a tubular stem 78 having an integral flangeportion 80, two rubber washers 82 and 84, and a nut and washer assembly86. The rubber washer 82 is placed on top of the flange and they areinserted into the interior of one pressure beam through the open end ofthe beam before it is formed into a continuous tube; and the stem 78 isinserted through the openings 68 and 74 of the pressure beams 60 and 62,respectively. The second rubber washer 84, and the nut and washerassembly 86 are similarly inserted in the second pressure beam andattached to the stem. The two rubber washers are clamped against the twosurfaces 66 and 70 of the pressure beams by tightening the nut assembly.Care should be taken that the stem 78 is only of sufficient length thatit does not extend past the nut in such a manner that it could rubagainst the surface 64 and cause an abrasion in that surface.

The two pressure beams are sealed together as shown at 88 to provide adurable connection between the two pressure beams. As the gaseous mediumis forced into one of the pressure beams, it will flow from one pressurebeam to the other until a uniform pressure is attained throughout theenitre support structure. Two corners of each pressure beam areconnected to two corners of a second and third pressure beam, in amanner similar to that described above, so that a six cornered supportstructure results.

In the above description and the attached drawings, a disclosure of theprinciples of this invention is presented, together with some of theembodiments in which the invention may be carried out.

I claim:

1. A support structure for a corner reflector comprising a first fourcornered inflatable tube, a second four cornered inflatable tube, athird four cornered inflatable tube, means for connecting said tubestogether so that when they are inflated they form a six cornered supportstructure, means for introducing an inflation medium into said supportstructure, and means for connecting a corner reflector having six outerapices to the six corners of the support structure.

2. An inflatable support structure comprising a first four corneredinflatable tube, a second four cornered inflatable tube, a third fourcornered inflatable tube, means for connecting said tubes together wheninflated thereby forming a six cornered support structure, and inletmeans for permitting said support structure to be filled with aninflation medium.

3. A support structure for a corner reflector comprising a firstsquare-shaped inflatable tube, a second squareshaped inflatable tube, athird square-shaped inflatable tube, means for connecting said tubestogether in such a manner that when they are inflated they form a sixcornered support structure, said means including means for connecting afirst two corners of the first tube to a first two corners of the secondtube, means for connecting a first two corners of the third tube to asecond two corners of the first tube, means for connecting a second twocorners of the third tube to a second two corners of the second tube,inlet means for permitting said support structure to be inflated with agaseous medium, and means for connecting a corner reflector having sixouter apices to the six corners of the support structure.

4. A six cornered support structure comprising a first inflatable tubeforming a first four cornered member when inflated lying in a firstplane, a second inflatable tube forming a second four cornered memberwhen inflated lying in a second plane, means for connecting the secondmember to the first member so that the second plane is perpendicular tothe first plane, a third inflatable tube forming a third four corneredmember when inflated lying in a third plane, means for connecting thethird member to the first and second members so that the third plane isperpendicular to the first and second planes, and valve meansoperatively associated with the support structure for admitting agaseous medium into said support structure.

5. The combination of claim 4 wherein each plane described by thetubular members is square-shaped and of equal dimensions, and means areprovided for connecting each corner of each tube to a corner of anothertube, at least two of said means having an opening forming a passagebetween the two tubes.

6. A six cornered support structure for a corner refleet-or comprising afirst inflatable tube forming a first four cornered member when inflatedlying in a first plane, a second inflatable tube forming a second fourcornered member when inflated lying in a second plane, means forconnecting the second member to the first member so that the secondplane is perpendicular to the first plane, a third inflatable tubeforming a third four cornered member when inflated lying in a thirdplane, means for connecting the third member to the first and secondmembers so that the third plane is perpendicular to the first and secondplanes, valve means for permitting the support structure to be inflatedwith a, gaseous medium, means for connecting each corner of each tube toa corner of another tube, at least two of said means having an openingforming a passage between the two tubes, and means for attaching acorner reflector having six outer apices to the six corners of saidstructure.

7. A collapsible six cornered support structure for a flexible cornerreflector comprising a first inflatable tube forming a firstsquare-shaped member when inflated lying in a first plane, a secondinflatable tube forming a second square-shaped member when inflatedlying in a second plane, means for connecting a first two corners of thefirst tube to a first two corners of the second tube so that the secondplane is perpendicular to the first plane, a third inflatable tubeforming a third square-shaped member when inflated lying in a thirdplane, means for connecting a first two corners of the third tube to asecond two corners of the first tube and means for connecting a secondtwo corners of the third tube to a second two corners of the second tubeso that the third plane is perpendicular to the first and the secondplanes, valve means operatively associated with the support structurefor admitting a gaseous medium into said support structure, at least twoof the means for connecting the corners of the tubes together having anopening forming a passage between the two tubes forming the corner, saidopenings permitting all the tubes to be inflated with the gaseousmedium, and means for attaching a flexible corner reflector having sixouter apices to the six corners of the support structure.

8. The combination of claim 7 wherein the support structure is comprisedof a non-extensible, gas-impervious, light-weight fabric material.

9. The combination of claim 8 wherein an adhesive is provided forconnecting the corners of the tubes together, said adhesive disposedbetween the surfaces of the tubes in such a manner that it surrounds theopening forming the passage, and a plurality of bolts connecting thetubes together are provided for reinforcing the connection.

10. The combination of claim 7 wherein the support structure iscomprised of a non-extensible, gas-impervious, light-weight plasticmaterial.

11. The combination of claim 10 wherein the means for connecting atleast two of the tubes together includes a tubular component insertedwithin the opening forming the passage between said tubes therebyconnecting the interior of one tube to the interior of a second tube,and a sealed portion connecting the tube-s together is provided forreinforcing the connection.

12. A collapsible support structure for a pliable corner reflectorcomprising a first inflatable square-shaped pressure beam having acircular cross-sectional area when inflated, a second inflatablesquare-shaped pressure beam having a circular cross-sectional area wheninflated, a third inflatable square-shaped pressure beam having acircular cross-sectional area when inflated, means for connecting saidpressure beams together to form a six cornered support structure, inletmeans for permitting said support structure to be inflated with agaseous medium, and means for connecting a pliable corner reflectorhaving six outer apices, and a plurality of reflecting surfaces to thesix corners of the support structure, so that as the structure isinflated with the gaseous medium the reflecting surfaces become taut andat least some of said surfaces mutually perpendicular to each other.

13. A flexible support structure comprising a first fourco rneredinflated continuous tube lying in a first plane, a second four-corneredinflated continuous tube lying in a second plane, a third four-corneredinflated continuous tube lying in a third plane, means for connectingthe corners of said inflated tubes to each other thereby forming aninflated six-cornered support structure, said three planes beingperpendicular to each other when the corners 7 8 of the tubes areconnected together, and valve means for FOREIGN PATENTS introducing aninflation medium into said support strue- 1223 184 1/60 France ture- 718516 11/54 Great Britain. References Cited by the Examiner 812:376 4 59Great Britain UNITED STATES PATENTS 2,534,716 12/50 Hudspeth et a1.343-18 CHESTER L. JUSTUS, Primary Examiner.

1. A SUPPORT STRUCTURE FOR A CORNER REFLECTOR COMPRISING A FIRST FOURCORNERED INFLATABLE TIBE, A SECOND FOUR CORNERED INFLATABLE TUBE, ATHIRD FOUR CORNERED INFLATABLE TUBE, MEANS FOR CONNECTING SAID TUBESTOGETHER SO THAT WHEN THEY ARE INFLATED THEY FORM A SIX CORNERED SUPPORTSTRUCTURE, MEANS FOR INTRODUCING AN INFLATION MEDIUM INTO SAID SUPPORTSTRUCTURE, AND MEANS FOR CONNECTING A CORNER REFLECTOR HAVING SIX OUTERAPICES TO THE SIX CORNERS OF THE SUPPORT STRUCTURE.
 2. AN INFLATABLESUPPORT STRUCTURE COMPRISING A FIRST FOUR CORNERED INFLATABLE TUBE, ASECOND FOUR CORNERED INFLATABLE TUBE, A THIRD FOUR CORNERED INFLATABLETUBE, MEANS FOR CONNECTING SAID TUBES TOGETHER WHEN INFLATED THEREBYFORMING A SIX CORNERED SUPPORT STRUCTURE, AND INLET MEANS FOR PERMITTINGSAID SUPPORT STRUCTURE TO BE FILLED WITH AN INFLATION MEDIUM.